Type Of Semiconductor Laser Research Articles

Recent developments in handheld and portable optosensing—A review

Recent developments in portable and handheld opto-chemical analytical instrumentation over the last decade (2000–2010) are reviewed. First, the characteristics of typical portable/handheld instrumentation are discussed from different points of view: in situ operation, low energy consumption, ease of use, and self-contained devices. These advancements have improved or hastened improvements in the development of miniaturized optoelectronic and optical components, mainly solid-state devices such as different types of semiconductor lasers, light-emitting diodes, and photodiodes. A brief review of advances in these components is also presented. The numerous examples of portable instrumentation presented have been classified according to direct-recognition and reagent-based sensing, and within these, by absorption and emission-based systems. The conclusion discusses some key trends and future perspectives for this technology.

Cavity soliton mobility in semiconductor microresonators above laser threshold

In this paper we investigated cavity soliton switching in a VCSEL type semiconductor laser which has been driven by homogeneous holding beam. Using quadratic fitting of the gain curve we studied the incoherent switching technique for the controlling of cavity solitons in a VCSEL-type laser and we show the cavity soliton spontaneous mobility in this type of injection.

All-optical frequency conversion using nonlinear dynamics of semiconductor lasers

When a semiconductor laser is subject to optical injection, it can enter the period-one dynamics through Hopf bifurcation. Under such nonlinear dynamics, equally and oppositely frequency-shifted optical signals from the injection emerge and are utilized for frequency conversion. Only a typical semiconductor laser is required as the conversion unit, where no pump or probe laser is necessary. The frequency shift can be continuously tuned by controlling the level or frequency of the injection. A bit-error ratio down to 10(-12) is observed with no or a slight power penalty for amplitude, frequency, and phase modulation at 2.5 Gbits/s, suggesting modulation format transparency of the system. Frequency down-, no-, and upconversion can be simultaneously achieved and individually selected, increasing the flexibility and reconfigurability of the system.

Characterization of the Main Semiconductor Laser Static and Dynamic Working Parameters From CW Optical Spectrum Measurements

We present a complete characterization of the work parameters of several types of semiconductor lasers. Static parameters as: power, linewidth and linewidth enhancement factor and also dynamic parameters such as: relaxation oscillations, relative intensity noise and damping rates are calculated using measurements of the optical spectrum of the lasers operated in continuous-wave mode. Methods for the calculation of these parameters are described and applied to the lasers under test by means of a single general setup and a single set of measurements

Phase-induced intensity noise in digital incoherent all-optical tapped-delay line systems

In this paper, the authors analyze conditions under which they can be certain on the intensity addition of a given device, such as tapped-delay lines, used in digital incoherent all-optical communication systems. A general expression for phase-induced intensity noise that is applicable to all types of semiconductor lasers is derived by defining an optical self-SNR expression that can be used to analyze and measure phase-induced intensity noise. The result shows that in order to have a minimal phase-induced intensity noise in most digital optical incoherent systems, a large optical self-SNR, e.g., 20 dB or more, is needed. This in turn is shown to place a limit on the maximum rate of processing in a typical incoherent optical system even neglecting the bandwidth limitation of the photodetector. Furthermore, it is shown that the maximum rate of processing depends on the laser autocorrelation function and laser coherence time

Characteristic of Self-Coupling Distance Meter using VCSEL

In developing an automation in processes, a demand for compact and simple distance measurement is increasing. A compact distance meter based on self-coupling effect of semiconductor laser has been studied. It is a compact and simple sensor with high accuracy as it consists of only a laser and a lens. However, a measurement error of this distance meter increases due to mode hop of FP type semiconductor laser. In this paper, a distance meter based on self-coupling effect using VCSEL is studied. It is confirmed that the mode hop for VCSEL does not happen and the distance meter using VCSEL can measure a distance. Furthermore, the distance meter using VCSEL with less optical output power can measure longer distance than that using FP laser.

Numerical stability maps of an optically injected semiconductor laser

Detailed experimental mappings of the dynamics of a Fabry–Pérot type semiconductor laser subjected to external optical injection along with parameters describing the injected laser have been published by Eriksson and Lindberg [J. Opt. B: Quantum Semiclass. Opt. 4 (2002) 149] and by Eriksson [Opt. Commun. 210 (2002) 343]. This paper reports on a numerical investigation of the injection experiments. By computing the largest Lyapunov exponent, the chaotic islands, periodic windows and locking ranges are compared in detail with the experimental results for three different operating points of the laser. The numerical results are in good agreement with the experiment once the linewidth enhancement factor is increased from the earlier reported value of 3.9±0.5 to about 6.7. The new value is confirmed by a re-measurement of the linewidth enhancement factor using a current modulation technique.

Combined x-ray diffraction/scanning tunneling microscopy study of segregation and interfacial bonding in type-II heterostructures

Appropriate control over the type-II band alignment between InAs and GaSb is important for a number of applications, including the further development of midinfrared (IR) semiconductor lasers and long-wavelength photodetectors. Accurate tailoring of interface structure and composition in such heterostructures grown by molecular beam epitaxy is nevertheless problematic for several reasons. Special challenges are posed by antimony segregation at the arsenide-on-antimonide interface, indium segregation at the antimonide-on-arsenide interface, and by the desire to selectively control the purity and types of interface bonds at either heterojunction. Here, we briefly review how cross-sectional scanning tunneling microscopy may be used to examine antimony and indium segregation with atomic-scale precision in type-II quantum wells, and then explain how such measurements suggest a unique structural interpretation for the residual strain exhibited by typical mid-IR semiconductor laser active regions in x-ray diffraction.

InAsSb/InAsSbP current-tunable laser with narrow spectral line width

The article describes the manufacture and testing of a new type of semiconductor laser working at low temperatures (12–100 K) in the wavelength range 3200–3300 cm-1. This kind of laser can be tuned in the modal range up to 6 cm-1 and is characterized by a narrow spectral line width (about 7 MHz).

Coexistence of thermal noise and squeezing in the intensity fluctuations of small laser diodes

The intensity fluctuations of laser light are derived from photon number rate equations. In the limit of short times, the photon statistics for small laser devices such as typical semiconductor laser diodes show thermal characteristics, even above threshold. In the limit of long-time averages represented by the low-frequency component of the noise, the same devices exhibit squeezing. It is shown that squeezing and thermal noise can coexist in the multimode output field of laser diodes. This result implies that the squeezed light generated by regularly pumped semiconductor laser diodes is qualitatively different from single-mode squeezed light. In particular, no entanglement between photons can be generated by use of this type of collective multimode squeezing.

A tunable single-mode 3.2 μm laser based on an InAsSb/InAsSbP double heterostructure with drive-current tuning range of 10 cm −1

A new type of semi-conductor laser with composition InAsSb/InAsSbP is described. This laser was produced for the absorption spectroscopy of atmospherically important molecules in the 3100 cm −1 region and tested using a closed-cycle He-cryostat in the temperature range 30–80 K. The optimal characteristics of the laser were found to be a heatsink temperature of 62 K and a drive current range of 50–350 mA. Under these conditions, the laser emits single-mode radiation in an exceptionally large wavenumber range of >10 cm −1. To test the laser, several experiments were carried out in which the rovibrational absorption spectra of CH 3Cl, NH 3, OCS and H 2O were measured.

Design Concepts for Coherent Arrays of High-Power Diode Lasers.

Characteristics of lateral phase control with a Talbot self-imaging cavity, which can offer lateral coherence among array type semiconductor lasers, is described. A Talbot cavity with a 1/4 Talbot distance can select a highest array mode, which is characterized by a double peak far-field pattern. So far, the number of broad area diodes that are coherently coupled with the highest array mode is limited around 10. Precise management of emission characteristics of emitters in arrays, and optimization of array fill factors could increase the number of phased arrays, resulting in higher brightness in the far-field.

Lasing Possibility in Rare-earth Element Doped Thiogallate Compounds

In this paper discussions based on the result of a pump-probe experiment are given on a possibility of application of the emission from Ce doped CaGa2S4 to production of a new laser. Existence of enough gain for laser action was clearly demonstrated from the analysis of the experimental result. Using the phonon-terminated character of this emission, construction of an unique laser having wide wavelength tunability covering violet to green region is thought to be possible. As far as optically pumped lasers are concerned, the only problem to be solved is to grow good single crystals having a suitable size (1×1×1 mm3 or more). In order to realize injection type semiconductor lasers with this material, we have to study conduction type and conductivity control technique together with a suitable epitaxial growth method for obtaining thin films of this material. It is pointed out that Ce doped SrGa2S4 and BaGa2S4 are also strong candidates for construction of similar lasers.

Nonlinear gain model and its application for numerical investigation of semiconductor lasers

The optimization of parameters and adequate methods of modeling for the creation of new types of semiconductor lasers with improved properties are required. In this work, a numerical model of gain is presented, which contains a complex description of the linear and nonlinear effects in an active layer. We show the more exact conformity of the given model to experimental data for large levels of light power and pumping currents. The original method of calculations of the total density states function for the quantum well (QW) laser is shown. The given expression has allowed us to reduce the model calculation time. ©1999 John Wiley & Sons, Inc. Microwave Opt Technol Lett 21: 474–477, 1999.

Modification of semiconductor laser diodes by focused ion beam milling

Focused ion beam (FIB) milling has been applied to improve and tailor the emission characteristics of Fabry-Perot type semiconductor lasers. Multi-mode commercial lasers operating at 780 nm were modified by sputtering 1 μm × 1 μm depressions into the top of the ridge waveguide with a 30 keV Ga + FIB. As the hole depth approaches the active layer, three effects on device operation were observed. First, a modest increase in laser threshold (≤ 20%) occurred without any accompanying change in the diode's current versus voltage characteristic. Second, overall emission was blue-shifted by up to 20 nm. Third, the perturbation introduced in the waveguide altered the mode structure of the emission spectrum. Single-mode operation with diminished mode-hopping could be promoted by the selective placement of the depressions along the length of the waveguide, which act as localized absorbers producing periodic modulations in the laser's spectral gain curve. Feedback regarding the progression of FIB structuring was achieved via in situ monitoring of the laser threshold and spectrum. The effect of the ion beam on light generation and propagation was characterized by sub-threshold electroluminescence measurements, which indicated a relative increase in absorption at longer wavelength after FIB processing.

Travelling wave model of a multimode Fabry-Perot laser in free running and external cavity configurations

We report the results of a numerical study of multimode behaviour of a Fabry-Perot laser. The model is based on travelling-wave equations for the slowly varying amplitudes of the counterpropagating waves in the cavity, coupled to equations for spatially dependent population inversion and polarization of a two-level active medium. Variations in the material variables on the scale of a wavelength are taken into account by means of an expansion in a Fourier series. Results are given for typical semiconductor laser parameters. Spatially distributed spontaneous emission noise and carrier diffusion are taken into account. The competing roles of spatial hole burning (SHE), spontaneous emission noise, and carrier diffusion in determining multimode behaviour are elucidated; with no carrier diffusion, spontaneous emission noise excites a large number of modes close to threshold, while SHE leads to a fixed number of significant lasing modes well above threshold. Carrier diffusion washes out the gratings in the material variables, and the resulting strengthening of the inter-mode coupling (cross-saturation) restores dominant single-mode emission well above threshold. We have also studied the effects of optical feedback and opportunities for mode selection with short external cavities; for an external cavity much shorter than the laser cavity length and a small field amplitude reflectivity coefficient, a single mode can be selected. For a large reflectivity coefficient, two groups of intracavity modes separated by the external cavity mode interspacing are selected. For an external cavity with a round trip time half that of the laser cavity, the laser can be forced with modest feedback to operate on two modes that are both quasiresonant with the external cavity. Mode selection is not found, even for weak feedback, when the external mode spacing is about 90% of the laser mode spacing.

新しい805nm半導体レーザーのレーザー血管形成術への応用性の検討

The authors studied on the feasibility of 805nm Laser produced by a new compact semiconductor laser equipment (Diomed 25, made in UK) to apply to laser angioplasty.The walls of fresh pig aorta and frozen human arteriosclerotic aorta were irradiated by this laser through bare-ended fibers at different power and exposure time, and the size of hole in terms of surface diameter and depth of holes created by vaporization was measured.The power of 25W was needed to vaporize and penetrate the aortic wall of both pig and human specimen.The pig aortic wall was penetrated by this laser irradiation for 1.2 to 18.4 seconds at 25W. The depth of vaporized hole ranged from 0.8 to 1.5mm. The volume of holes ranged from 0.224 to 1.26cmm. The human aortic wall was penetrated when irradiated through bulb type fiber for 2 to 5 seconds at 25W. The average diameter of a hole was 1.24mm, and the average depth was 2.3mm. The human aortic wall was vaporized when irradiated through a conical type fiber for 1 to 3 seconds at 25W, and the average diameter of a hole was 1.12 mm, and its depth was 1.85 mm in average.Once vaporization of aortic wall occurs, the time necessary to vaporize the wall became shorter for the second time. It is assumed that minute carbon particles sticked or adhered to the surface of the tip of a laser fiber from the first lasing produced more heat to the aortic wall, and thus the necessary time for vaporization was shortened.It seems to be important to keep this phenomenon in mind to apply laser to stenotic arterial wall in order to control optimal laser energy.It seems to be warranted to test the effect of a ceramic tip for contact irradiation of this new type of semiconductor laser before applying to clinical case.

Low threshold current density operation of GaInAsP-InP laser with multiple reflector microcavities

We propose and demonstrate a new type of semiconductor laser having multiple reflector microcavities for the purpose of low threshold current operation. Very uniform multiple reflector microcavity structure was fabricated by electron beam (EB) lithography and selective wet chemical etching. Due to multiple reflection effect, threshold current density as low as 310 A/cm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> (threshold current of 30 mA) was obtained at room temperature with the total cavity length of 64 μm and the cavity width of 200 μm.

Investigation of an electron-beam microgun using a microtips array

A microtip field-emission electron microgun of a few cm3 has been developed for a novel type of semiconductor laser. The electron source is provided by an array of a field emissive microtips cathode each of 1.4 μm base diameter. The source current–voltage characteristic has been determined and its geometrical characteristics have been measured by collecting electrons on a phosphor screen in a region of constant electric field. We have observed that about 100 μA are typically emitted for gate-cathode voltage (VGC) of 80 V with a half-aperture angle of 28°. Beam focusing is then realized by two electrostatic lenses: a ‘‘thin hole lens’’ and a quadrupole lens. Using a cathode a 70×500 μm2 rectangular spot on a 10 kV biased anode has been obtained which yields a power density of about 3 kW/cm2. Less than 20% of the total electron beam (current) is lost in the electrostatic optics.

REACTIVE ION ETCHING OF III–V SEMICONDUCTORS

Anisotropic dry etching by a number of different techniques is widely employed in III–V compound semiconductor technology for pattern transfer, device isolation, mesa formation, grating fabrication and via hole etching. In this paper we review the different dry etching techniques, the plasma chemistries employed for III–V materials and electrical and optical changes to the near-surface of the etched sample. We give examples of the use of dry etching in fabrication of heterojunction bipolar transistors, field effect transistors and various types of semiconductor lasers. Particular attention is paid to the characteristics of Electron Cyclotron Resonance discharges operating at high ion densities (≥5×1011 cm −3) and low pressure (~1 mTorr) with low ion energies (≤15 eV ) which are ideally suited for dry etching of III–V semiconductors.